Donkey
was introduced into the Americas soon after its discovery in the 15th
century. However, there is no historical consensus on how they spread
across the continent. In a previous study, two distinct genetic pools
(Clusters A -Southern part - and B -Northern part of South America and
Central America) were identified, with likely confluence in Colombia.
The aim of this study was to evaluate whether the main genetic diversity
parameters, such as gene diversity (GD) and allelic richness (k), or
the relative contributions of various breeds to these parameters are
useful indicators to give genetic support to historical information on
putative routes of the spreading of donkeys across the American
continent. In full agreement with historical sources suggesting that
Greater Antilles were the first breeding nucleus, both total
contributions to gene diversity (gGDT) and to allelic richness (CT(k))
showed a higher ability to identify the "abundant centre" of the
species on the Continent. Even though there are historical reports
suggesting various entry points of the donkey into the continent (e.g.
in Brazil), these parameters suggested that, in our dataset, the Cuban
donkey population was the more likely representative of the first
breeding nucleus of the species. Central and South American donkey
populations in the surroundings of the Caribbean Gulf would more likely
be early derivatives of Antillean donkey. The strong North-South genetic
structure was confirmed for the American donkey metapopulation. Current
analyses suggest that populations classified into Cluster A (South) are
essentially a sample of the genetic background of Cluster B (North).
The Andean route had the highest importance in the formation of the
South American populations. The extinction of either population
belonging to Cluster B could lead to a decrease in overall genetic
diversity both at the gene diversity level (negative gGDT values) and the allelic richness level (positive CT(k)
contributions). The opposite pattern is found for populations belonging
to Cluster A. The extinction of the populations belonging to Cluster B
would decrease the overall American donkey gene diversity in roughly 8%
and would dramatically affect the number of alleles in the
metapopulation (19.1%). However, the extinction of the donkey
populations classified into Cluster A would increase overall gene
diversity by 2.2%. Although, the genetic scenario of each individual
population varies substantially, the joint conservation of the donkey
populations classified into both Clusters A and B is highly advised.